This multicenter, randomized, double-blind, parallel, placebo controlled study in asthmatic patients. Patients will be entered into a 2 week open, label, run-in phase in which patients will be administered Aerobid M 500 mcg twice daily without an Aerochamber and as needed albuterol for asthmatic exacerbations in order to familiarize the patients with the procedures used in the study and to assess compliance. Upon completion of the run-in phase, patients will be randomized into the 6 week, double-blind phase of the study which consists of 7 different treatment arms of Aerobid 250 mcg, 500 mcg, and 1000 mcg twice a day with or without an Aerochamber or placebo.